1. Field of the invention
The present invention relates to ink jet printheads manufactured with photoimageable layers, and more particularly to a support structure for the nozzle plate of an ink jet printer printhead, particularly useful for high-resolution printheads, and the method for manufacturing the structure.
2. Description of the Related Art
Ink jet printers are in wide use due to their low cost of operation, low energy use and quiet operating features. Ink jet printing involves ejection of tiny ink droplets through small nozzles in a controlled manner to create the desired image. Ink is supplied from an ink reservoir to a printing head, which includes various passageways from the reservoir to the nozzle orifice. Energy is applied to the ink from an ink droplet generator near each orifice, which may include the application of electrostatic attraction, the application of oscillating forces from piezo elements, the application of heat from heating elements or the like.
For creating a high print quality, the ink droplets reaching the receiving media should be of consistent volume and shape, and should strike the receiving media at a known angle to impart a pixel of desired size and shape on the media. To control the characteristics of the ink droplets ejected onto the receiving media, such as the size and shape of the ink droplet and the trajectory of the droplet towards the media, a nozzle plate is provided over the underlying printhead structure. The underlying structure defines various ink conducting voids in the material layers, such as ink vias, ink channels and firing chambers. Ink vias are larger volume ink flow paths supplying ink from a reservoir to a number of ink supply channels. The ink supply channels direct ink to the individual firing chambers beneath each of the nozzles. The ink droplet generator acts on the ink in the firing chamber, causing the ink to be ejected from the nozzle. By selectively activating individual ink droplet generators, the desired pattern of ink can be applied to the receiving surface, such as a sheet of paper, to create the desired image, which may be a letter, number, symbol, part of a picture or the like. The growing demand for high quality color printing places even greater demands on the precision of pixel deposition on the receiving surface.
In a known method for creating a printhead, laser ablation is used to form the ink channels, firing chambers and nozzles in a nozzle plate. Grit blasting is used to create an ink via in a heater chip. The nozzle plate is then applied to the heater chip. If properly aligned, a firing chamber is disposed directly beneath each nozzle, and ink channels receive ink from the ink via, and supply ink to each firing chamber. Accurately positioning the nozzles over the underlying structure can present manufacturing challenges, and improperly positioned nozzles can result in printing deficiencies.
U.S. Pat. No. 6,045,214 entitled xe2x80x9cInk Jet Printer Nozzle Plate Having Improved Flow Feature Design And Method Of Making Nozzle Platesxe2x80x9d discloses a nozzle plate and a method for making a nozzle plate which includes laser ablating ink flow channels, firing chambers, nozzle holes and ink supply regions in a polymeric film made of a polymeric material layer, an adhesive layer and a protective layer. The protective layer is removed, and the nozzle plate is attached to a semiconductor substrate using the adhesive layer.
Recent improvements in the resolution of images created by ink jet printers have been widely appreciated by users of the printers, but have created additional manufacturing difficulties for printer suppliers. Resolution in the printer art may be defined as the number of ink droplets or xe2x80x9cdotsxe2x80x9d which can be generated in one square inch of printing field. Thus, a resolution of 600 dpi (dots per inch) requires the capability of ejecting 600 droplets of ink in a one square inch area. Higher resolution, i.e. a greater number of smaller ink droplets per area, results in a more clear print, with finer, more defined lines. Again, the demand for better color printing capabilities has driven the need for higher resolution printheads
Each nozzle opening defines a single ink droplet. Higher resolution requires not only a higher concentration of nozzles in the nozzle plate, but also a higher concentration of firing chambers, ink channels, ink vias and the like in the structure underlying the nozzle plate. With the increased nozzle concentration required for higher resolution printers, and the need for an increased number of associated underlying firing chambers, ink channels and ink vias, the manufacture of nozzle plates has become more complex and difficult.
In a more recently developed, preferred method for making a printhead, the ink via in the heater chip is created by a grit blast process, and the nozzle plate is made in two thin, superimposed layers. First and second photo imageable layers are provided, with ink channels and firing chambers created in the first layer, and the ink nozzles created in the second layer. The photo imageable layers may be manufactured by processes that include the use of positive or negative photoresist materials, with a suitable photomask applied thereto, and subsequent exposure and development of the photoresist layer. Depending upon the selection of materials and the type of photoresist used (positive or negative), a positive or negative photomask is used, and the exposure and development process hardens either the masked or unmasked areas. Subsequent processing in a chemical bath dissolves the unhardened material, creating the desired ink conducting void or nozzle in the layer.
Precisely located ink channels, firing chambers and nozzles can be made utilizing this method. Using a multilayer structure having first and second photo imageable layers results in a better heater to nozzle alignment accuracy than in early methods of placing a laser ablated polyimide nozzle plate onto a grit blasted heater chip. Nozzle plate assemblies manufactured using photoimagable layers are also desirably thin. However, due to the extremely thin nature of the nozzle plate or second layer, and the lack of supporting structure beneath the nozzle plate in the first layer containing the various ink conducting voids, especially in printheads for higher resolution printers, there is a tendency for the second imageable layer to cave in over the ink via, as a result of the large span from one side of the underlying cavity to the other side thereof.
Therefore, what is needed is a support matrix for the nozzle plate of a photoimageable printhead for an ink jet printer, and a manufacturing process to create the printhead.
The present invention provides an imageable support matrix for an ink jet printhead, and a manufacturing method therefor, which provides increased areas of support beneath the printhead nozzle plate, and is particularly useful for printheads in higher resolution printers. support beneath the printhead nozzle plate, and is particularly useful for printheads in higher resolution printers.
The invention comprises, in one form thereof, a method of forming an ink jet printhead comprising providing a substrate; applying a first layer of imageable material on the substrate; masking the applied first layer of imageable material; developing the masked first layer of imageable material to provide ink conducting voids in the first layer of imageable material and hardened areas of support; creating an ink via in the substrate by removing material from the substrate and from the first layer of imageable material; applying a second layer of imageable material on the first layer of imageable material; and forming nozzles in the second layer of imageable material.
The invention comprises, in another form thereof, a method of forming an ink jet printhead comprising providing a substrate; creating an ink via in the substrate by removing material from the substrate; applying a first layer of imageable material on the substrate, including applying the imageable material over the ink via; masking the applied first layer of imageable material; developing the first layer of imageable material to provide ink conducting voids in the first layer of imageable material and openings through the imageable material communicating with the ink via; applying a second layer of imageable material on the first layer of imageable material; and forming nozzles in the second layer of imageable material.
The invention comprises, in yet another form thereof, a method of forming an ink jet printhead comprising providing a substrate; creating an ink via through the substrate; providing a first layer of imageable material; developing the first layer of imageable material to create ink conducting voids and support structures up to the ink via; and providing a second layer of imageable material on the first layer of imageable material, said second layer of imageable material including nozzles therein.
The invention comprises, in a further form thereof, an ink jet printhead comprising; a substrate including an ink via therein; a first layer of imageable material, the first layer of imageable material having ink conducting voids therein and defining support structures adjacent the ink via; and a second layer of imageable material disposed on the first layer of imageable material, the second layer of imageable material including ink jet nozzles therein.
The invention comprises, in still another form thereof an ink jet printhead comprising a substrate having an ink via; a first layer of imageable material defining ink conducting voids therein, and including support structures adjacent the ink via; and a second layer of imageable material supported by the first layer of imageable material and having nozzles therein. The ink jet printhead is manufactured by applying the first layer of imageable material on the substrate; creating in the first layer of imageable material ink conducting voids; removing material from the substrate and from the first layer of imageable material to create the ink via; applying the second layer of imageable material on the first layer of imageable material; and developing the second layer of imageable material to create the nozzles.
The invention comprises, in a still further form thereof an ink jet printhead comprising a substrate having an ink via; a first layer of imageable material defining ink conducting voids therein, and including support structures adjacent the ink via; and a second layer of imageable material supported by the first layer of imageable material and having nozzles therein; the ink jet printhead manufactured by; creating an ink via in the substrate; applying the first layer of imageable material over the substrate and the ink via in the substrate; masking the first layer of imageable material; developing the first layer of imageable material to define the ink conducting voids, the support structures and an opening to the ink via; applying the second layer of imageable material over the first layer of imageable material; and developing the second layer of imageable material to create the nozzles.
An advantage of the present invention is providing a high-resolution printhead less prone to nozzle plate collapse than previously known structures.
Another advantage is providing a manufacturing method for a high-resolution printhead, which utilizes known techniques and materials in a way to increase nozzle plate support in the completed printhead.
A further advantage of the present invention is reducing the length of unsupported, open spans beneath the nozzle plate layer of a multi-layer printhead, and providing nozzle plate support structures adjacent and/or spanning the ink via opening beneath the nozzle plate.